1. Field of the Invention
This invention relates to magnetic tape cassettes, and more specifically to a novel audio compact cassette which is equal to or smaller than the "Philips" type magnetic tape cassette in size.
2. Background Art
Recently, cassette tape recorders have been decreased both in size and in weight. Also magnetic tape cassettes for use with these miniaturized recorders have also been miniaturized. In the field of audio technique also, there has been a strong demand for the provision of a magnetic tape cassette which can suitably record and reproduce signals with high quality and high density for a long period of time. In order to meet this requirement, there has been proposed a magnetic tape cassette operated according to a digital system such as a pulse modulation (PCM) system. In a digital system, unlike an analog system, the recording and reproducing operation is carried out with input signals converted into pulse signals. In the magnetic tape operated according to the digital system, the recording frequency band must be about five times as wide as that of a conventional audio magnetic tape. Therefore, a larger video tape cassette whose recording frequency band is wider than that of an audio compact cassette is extensively employed.
Video tape cassettes, except for special ones, are operated according to a rotary magnetic head system. The video tape cassette has a guard panel which is adapted to close the opening formed in the front part of the cassette, and is swingable upwardly of the cassette. That is, the magnetic tape cassette operated according to the digital system is used for the recording and reproducing operation of a high-density wide frequency band having a short recording wavelength in comparison with the conventional audio compact cassette. Therefore, the structure of the cassette should be such that the magnetic tape therein is sufficiently protected.
A magnetic tape cassette satisfying the above-described requirement, i.e., a magnetic tape cassette to which the technical concept of the invention is applied is suitable for audio devices employing a relatively wide frequency band recording and reproducing system similarly as in the above-described video tape cassette. The magnetic tape cassette is a small one which is equal to or smaller than the conventional audio compact cassette in size. Accordingly, it can be expected that the magnetic tape cassette is carried and used outdoors similarly as or perhaps more frequently than in the case of the conventional audio compact cassette. Therefore, the magnetic tape cassette should be designed so as to positively prevent the difficulty that, when the cassette is carried about, the cassette is vibrated, so that the magnetic tape becomes slackened and is jammed.
One example of the magnetic tape cassette satisfying this condition has a locking member which locks the hubs on which the magnetic tape is wound, when the cassette is not in use, and releases the hubs when the cassette is in use (operated). The locking member is designed as follows. The locking member is biased towards the hubs by a spring. When the cassette is not in use, the protrusion of the locking member is abutted against the hubs, and when it is used, the protrusion is disengaged from the hubs. As the cassette is miniaturized as was described before, the components are also formed smaller, which makes it difficult to combine them together to form the cassette. As the locking member is combined with the cassette body while being urged by the spring, it is liable to come off. Thus, the locking member is one of the factors which make it difficult to assemble the magnetic tape cassette.
The spring for biasing the locking member is coupled to the base part of the locking member, and its legs are slidably supported on the front wall of the lower half case or the upper half case. As the upper and lower half cases are made of resin such as ABS resin which is inexpensive and can be readily molded, sometimes the front wall is scraped by the legs of the spring, to form shavings. The shavings thus formed may attach to the magnetic tape to cause dropouts. That is, the shavings may make it impossible to record or reproduce signals with high accuracy.